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Troubleshooting: Paint Cracking and Flaking

Alligatoring

DESCRIPTION

Paint alligatoring is a form of paint failure where large cracks form in the surface layer only, resulting in the appearance of an alligator hide.

POSSIBLE CAUSES

Applying paint over a porous, unsealed surface, resulting in rapid absorption and improper film formation.

Applying paint in high heat or very low humidity, causing solvent to evaporate too rapidly.

Applying second coat of paint before first coat has completely dried.

Applying a harder, less flexible paint or coating over a softer or more flexible one (a brittle oil-based paint over a more flexible latex paint).

SOLUTION

To fix paint alligatoring remove all loose paint, sand edges smooth, then prime and seal the surface with an appropriate primer for the specific application or surface to be painted. Once primer is completely dry, apply a fresh coat of paint.

Blocking

DESCRIPTION

Paint blocking is the unwanted sticking together of two painted surfaces when they are pressed together (such as a door sticking to the door jamb or a window sash sticking to the frame), or a painted surface sticking to another surface, such as weather stripping.

POSSIBLE CAUSES

Insufficient dry time of the paint before closing doors or windows.

Use of a low-quality semi-gloss or gloss paint.

SOLUTION

To fix paint blocking remove all loose paint, sand edges smooth, then prime and seal the surface with an appropriate primer for the specific application or surface to be painted. Once primer is completely dry, apply a fresh coat of paint.

Follow label instructions regarding dry time of the paint. Acrylic latex paint generally has better early block resistance than vinyl latex or alkyd (oil-based) paints, although alkyd paints do develop better block resistance over time. The application of talcum powder, petroleum jelly or wax can relieve persistent blocking of the paint.

Flaking

DESCRIPTION

Flaking is the lifting of paint from the underlying surface in the form of flakes. Flaking paint is normally preceded by cracking or checking and can occur over different surfaces.

POSSIBLE CAUSES

Cracking of exterior wood or plywood as it expands and contracts in response to changes in temperature and humidity, which is transmitted through the paint.

Poor paint penetration, especially on wood with an excessive amount of hard-/flat-grain pattern, which is smooth, hard and nonporous.

Poor surface preparation.

Applying the paint too thinly.

SOLUTION

To fix flaking paint remove all loose flaking paint, sand edges smooth, then prime and seal the surface with an appropriate primer for the specific application or surface to be painted. Once primer is completely dry, apply a fresh coat of paint.

Follow label instructions regarding dry time of the paint. Acrylic latex paint generally has better early block resistance than vinyl latex or alkyd (oil-based) paints, although alkyd paints do develop better block resistance over time. The application of talcum powder, petroleum jelly or wax can relieve persistent blocking of the paint.